CN106026162A - Double-input single-tube Boost-type photovoltaic interface converter and control method thereof - Google Patents

Abstract

The invention discloses a double-input single-tube Boost-type photovoltaic interface converter and a control method thereof. The converter includes a first input filtering capacitor, a second input filtering capacitor, an output filtering capacitor, an inductor, a switch transistor and a diode, one end of the switch transistor is connected to one end of the inductor and one end of the second input filtering capacitor, the other end of the inductor is connected to one end of the first input filtering capacitor, the other end of the second input filtering capacitor is connected to an anode of the diode, a cathode of the diode is connected to one end of the output filtering capacitor, and the other end of the output filtering capacitor, the other end of the switch transistor, and the other end of the first input filtering capacitor are connected together. The converter of the present invention achieves independent MPPT controls of two photovoltaic strings by adjusting a duty ratio and an output current. Besides, as compared with the existing double-input Boost converter, the converter provided by the present invention is lowest in the number of the components, therefore the efficiency and integration degree of a distributed photovoltaic power generation system are significantly improved, and the system cost is reduced.

Description

Dual input single tube Boost type photovoltaic interface changer and control method thereof

Technical field

The present invention relates to a kind of photovoltaic interface changer, be specifically related to a kind of dual input single tube Boost type photovoltaic interface changer and control thereof Method processed.

Background technology

Development distributed photovoltaic grid-connected system has become one of countries in the world Important Action promoting energy-saving and emission-reduction.In order to suppress electric Multimodal effect during parameter mismatch, promotes the electric energy conversion efficiency of photovoltaic array, and distributed photovoltaic grid-connected system is frequently with many string datas Framework, as shown in Figure of description 2.But, this framework needs multiple photovoltaic interface changers, and number of elements is many, relatively costly, And efficiency and integrated level are difficult to promote.To this end, research worker proposes various multi input photovoltaic interface converter topology.Although these sides Case is capable of the independent MPPT of each photovoltaic string, improves system effectiveness and integrated level, but power tube quantity is the most more, this Limit the further lifting of systematic function.

Summary of the invention

Goal of the invention: the invention aims to solve deficiency of the prior art, it is provided that a kind of number of elements is few, it is distributed to improve The efficiency of photovoltaic generating system and integrated level, and reduce system cost, and by regulation dutycycle and output electric current, achieve two respectively The dual input single tube Boost type photovoltaic interface changer of the independent MPPT control of individual photovoltaic string and control method thereof.

Technical scheme: a kind of dual input single tube Boost type photovoltaic interface changer of the present invention, including the first input filter capacitor C_i1, the second input filter capacitor C_i2, output filter capacitor C_o, inductance L, switching tube S and diode D, described switching tube S's One end is connected to inductance L and the second input filter capacitor C_i2One end, the other end of described inductance L connects the first input filter Ripple electric capacity C_i1One end, described second input filter capacitor C_i2The other end connect and have the anode of diode D, described diode D Negative electrode connect have output filter capacitor C_oOne end, described output filter capacitor C_o, switching tube S, the first input filter capacitor C_i1 The other end jointly connect.

Further, described first input filter capacitor C_i1, the second input filter capacitor C_i2Input respectively with two photovoltaics series winding Connect；Described output filter capacitor C_oConnect and have DC/AC transducer.

Further, the output electric current of the photovoltaic string that described inductance L side joint enters is more than the output electric current of another photovoltaic string.

The invention also discloses the control method of above-mentioned a kind of dual input single tube Boost type photovoltaic interface changer, utilize controlled quentity controlled variable to switch The driving signal of pipe SThe MPPT realizing first photovoltaic string controls；By the output electric current of interface converterTransfer controlled quentity controlled variable to, The MPPT completing another one photovoltaic string by latter stage grid inverter controls.

Further, concrete rate-determining steps includes:

MPPT for first photovoltaic string controls: first distinguish output voltage and the electric current of this photovoltaic string in Sampling Interface changer, Voltage reference u is constantly adjusted by power calculation_pv1,ref, by u_pv1,refWith sampled voltage u_pv1The error signal obtained sends into actuator 1, The signal of actuator 1 output sends into drive circuit through PWM, produces PWM drive signal, for controlling switching tube S's Open shutoff, thus the MPPT realizing photovoltaic module 1 controls；

MPPT for another photovoltaic string controls: adjust electricity again by sampling photovoltaic string output voltage, electric current and power calculation Pressure benchmark u_pv2,ref, by u_pv2, and sampled voltage u_pv2The error signal obtained sends into actuator 2, obtains exporting the base of electric current loop after regulation Calibration signal i_o,ref, this controls outer shroud for MPPT；Further, by i_o,refWith output current sampling signal i_oThe error signal obtained is sent Enter actuator 3, through overregulating the magnitude reference obtaining grid-connected current ring, then by this signal and the unit of frequently homophase same with line voltage Sinusoidal signal is multiplied and obtains reference signal i of grid-connected current_g,ref, by this reference signal and grid-connected current sampled signal i_g, seek the error that difference obtains Signal sends into actuator 4, it is achieved the control of grid-connected current ring；Finally, the sinusoidal modulation signal of actuator 4 output is adjusted through SPWM System sends into drive circuit, produces SPWM and drives signal, opens shutoff for control 4 switching tubes of rear class DC/AC changer, It is achieved thereby that the MPPT of photovoltaic module 2 controls.

Further, described actuator 1, actuator 2, actuator 3, actuator 4 use the linear regulators such as PI, PID.

Beneficial effect: the changer of the present invention, by regulation dutycycle and output electric current, achieves the independent MPPT of two photovoltaic strings respectively Control.And compared with existing dual input Boost, the number of elements of this changer has reached minimum, therefore can significantly carry The efficiency of high distributed photovoltaic generating system and integrated level, and reduce system cost.

Accompanying drawing explanation

Fig. 1 is the inverter main circuit topological diagram of the present invention；

Fig. 2 is two string data Organization Charts of the prior art；

Fig. 3 is the power tube current oscillogram in changer of the present invention；

Fig. 4 is the Control system architecture schematic diagram of the present invention；

Fig. 5 is the present invention MPPT control block diagram to a photovoltaic string；

Fig. 6 is the present invention MPPT control block diagram to another photovoltaic string；

Fig. 7 is simulating, verifying electrical block diagram of the present invention；

Fig. 8 is the voltage stress oscillogram of the switching tube in simulating, verifying and diode；

Fig. 9 is the current stress oscillogram of the switching tube in simulating, verifying and diode；

Figure 10 is the current stress oscillogram of the inductance in simulating, verifying；

Figure 11 is the voltage stress oscillogram of the electric capacity in simulating, verifying；

Figure 12 is the output voltage waveform of the photovoltaic module 1 in simulating, verifying；

Figure 13 is the output voltage waveform of the photovoltaic module 2 in simulating, verifying；

Figure 14 is the output current wave figure of the changer in simulating, verifying.

Detailed description of the invention

A kind of dual input single tube Boost type photovoltaic interface changer of the present invention is as shown in dotted line frame in Fig. 1.Concrete, this change Parallel operation includes the first input filter capacitor C_i1, the second input filter capacitor C_i2, output filter capacitor C_o, inductance L, switching tube S and Diode D, one end of described switching tube S is connected to inductance L and the second input filter capacitor C_i2One end, described inductance L The other end connect have the first input filter capacitor C_i1One end, described second input filter capacitor C_i2The other end connect have diode The anode of D, the negative electrode of described diode D connects output filter capacitor C_oOne end, described output filter capacitor C_o, switching tube S, First input filter capacitor C_i1The other end jointly connect.Described first input filter capacitor C_i1, the second input filter capacitor C_i2's Input is connected with two photovoltaic strings respectively；Described output filter capacitor C_oConnect and have DC/AC transducer.

It can be seen that compared with the conventional architectures shown in accompanying drawing 2, this changer equally realizes the access of two photovoltaic strings, and realizes The independent MPPT of each string controls, but the equal drop by half of quantity of power tube and inductance, greatly improve the integrated level of system, will Reduce cost.

Changer to the present invention shown in Fig. 1 carries out specificity analysis below:

1. voltage gain

During stable state, dual input Boost is switch periods T_sInterior work process is divided into two mode.As t ∈ [0, DT_s) Time, switching tube S is open-minded, the terminal voltage of inductance L (reference direction be left+, right-) be:

u_L=U_PV1 (1)

As t ∈ [DT_s,T_s) time, switching tube S turns off, has:

u_L=U_PV1+U_PV2-U_o (2)

According to voltage-second balance principle, then:

DU_PV1+(U_PV1+U_PV2-U_o) (1-D)=0 (3)

Abbreviation can obtain the input of dual input Boost, output voltage relation is:

$U_o=\frac{U_{PV1}+(1-D)U_{PV2}}{1-D}=\frac{U_{PV1}}{1-D}+U_{PV2}---\left(4\right)$

It can be seen that output voltage U_oMinima be (U_PV1+U_PV2)。

2. the voltage stress of power tube

Switching tube S turn off time, its terminal voltage (reference direction be upper+, under-) be:

$u_S=U_o-U_{PV2}=\frac{U_{PV1}}{1-D}---\left(5\right)$

When switching tube S opens, diode terminal voltage (reference direction be right+, left-) be:

$u_D=U_o-U_{PV2}=\frac{U_{PV1}}{1-D}---\left(6\right)$

3. the current stress of power tube

If thinking P₁+P₂=P_o, P₁=U_PV1I_PV1, P₂=U_PV2I_PV2, I_PV2=I_o.Then have:

I_PV2=(1-D) I_PV1 (7)

$I_{PV1}=\frac{I_o}{1-D}=\frac{I_{PV2}}{1-D}---\left(8\right)$

So, this changer is wanted normally to work, it is desirable to the output electric current of two power supplys must is fulfilled for following condition: I_PV1＞ I_PV2。 Power tube current waveform is as shown in Figure 3.When switching tube S opens, its current average is:

$I_S={\mathrm{DI}}_{PV1}=\frac{{\mathrm{DI}}_o}{1-D}---\left(9\right)$

When switching tube S turns off, the current average flowing through diode D is:

I_D=(1-D) I_PV1=I_o=I_PV2 (10)

Table 1 show dual input Boost and the performance comparison of two traditional Boost parallel-connection structures that the present invention proposes.

Table 1 Performance comparision

P in upper table_max1And P_max2Represent photovoltaic string 1 and the peak power output of photovoltaic string 2 respectively.

MPPT control method below for this changer is described in further detail:

Traditional single input photovoltaic interface changer is by regulation dutycycle, it is achieved input voltage U_PVClosed loop control, finally realize light The MPPT of volt battery controls.But, single tube two inputs Boost needs to realize the MPPT control of two photovoltaic cell strings simultaneously , there are two outputs the most all the time in systemWithBut, it only has a controlled quentity controlled variableTwo cannot be controlled simultaneously Output, therefore a controlled quentity controlled variable must be found again.To this end, single tube two inputs Boost will use MPPT as shown in Figure 4 Control strategy: utilize controlled quentity controlled variableThe MPPT realizing photovoltaic string PV1 controls；Electric current will be exportedTransfer controlled quentity controlled variable to, by Latter stage grid inverter completes the MPPT of photovoltaic string PV2 and controls.Fig. 5 and Fig. 6 gives photovoltaic interface system under MPPT pattern Structure and control block diagram.

The correctness analyzed for proof theory, constructs the emulation model machine of a 420W/100kHz, as shown in Figure 7 further.Figure In, the electric parameter of photovoltaic module 1 and 2 is shown in Table 2, table 3.

The parameter of table 2 PV1

The parameter list of table 3 PV2

Fig. 8 Figure 14 gives system emulation result, the data one that wherein simulation parameter of photovoltaic cell component provides with table 2, table 3 Cause.Fig. 8-Figure 11 is that interface converter is correlated with the simulation result of electric stress.It can be seen that Fig. 8 breaker in middle pipe S and diode D Voltage stress is respectively as follows: 59.893V and 56.04V；In Fig. 9, current stress is respectively as follows: 4.5554A and 4.3971A.Electricity in Figure 10 The current stress of sense is 8.9453A, and in Figure 11, the voltage stress of electric capacity is 90.548V.These simulation results match with theory analysis. Figure 12-Figure 14 gives the output current simulations waveform of photovoltaic module and changer.It can be seen that the input voltage control of photovoltaic module 1 Being made as 31.207V, the input voltage of photovoltaic module 2 controls as 31.828V.Obviously, this changer achieves two photovoltaic strings respectively MPPT controls, thus demonstrates the feasibility of MPPT control strategy of the present invention.

The present invention proposes a kind of novel dual input Boost photovoltaic interface changer, and uses Saber software to carry out simulating, verifying. Result of study shows, this changer can realize the independent MPPT of two photovoltaic strings and control, and have that number of elements is few, integrated level is high, Low cost and other advantages.It should be noted that two photovoltaic strings that this changer accesses must are fulfilled for following use condition: if by inductance side The photovoltaic string accessed is PV1, and the photovoltaic that booster diode side joint enters is PV2, then the output electric current of PV1 have to be larger than the output of PV2 Electric current, otherwise this changer cannot normally work.

The above, be only presently preferred embodiments of the present invention, the present invention not makees any pro forma restriction, although the present invention Disclosed above with preferred embodiment, but it is not limited to the present invention, any those skilled in the art, without departing from this In inventive technique aspects, when the technology contents of available the disclosure above makes a little change or is modified to the equivalence enforcement of equivalent variations Example, as long as being the content without departing from technical solution of the present invention, according to the technical spirit of the present invention above example is made any simply Amendment, equivalent variations and modification, all still fall within the range of technical solution of the present invention.

Claims (6)

1. a dual input single tube Boost type photovoltaic interface changer, it is characterised in that: include the first input filter capacitor C_i1、 Second input filter capacitor C_i2, output filter capacitor C_o, inductance L, switching tube S and diode D, described switching tube S's One end is connected to inductance L and the second input filter capacitor C_i2One end, the other end of described inductance L connect have first defeated Enter filter capacitor C_i1One end, described second input filter capacitor C_i2The other end connect and have the anode of diode D, described two The negative electrode of pole pipe D connects output filter capacitor C_oOne end, described output filter capacitor C_o, switching tube S, first input Filter capacitor C_i1The other end jointly connect.

A kind of dual input single tube Boost type photovoltaic interface changer the most according to claim 1, it is characterised in that: described First input filter capacitor C_i1, the second input filter capacitor C_i2Input be connected with two photovoltaic strings respectively；Described output filter Ripple electric capacity C_oConnect and have DC/AC transducer.

A kind of dual input single tube Boost type photovoltaic interface changer the most according to claim 1, it is characterised in that: described The output electric current of the photovoltaic string that inductance L side joint enters is more than the output electric current of another photovoltaic string.

4. according to the controlling party of a kind of dual input single tube Boost type photovoltaic interface changer described in claim 1-3 any one Method, it is characterised in that: utilize the driving signal of controlled quentity controlled variable switching tube SThe MPPT realizing first photovoltaic string controls； By the output electric current of interface converterTransfer controlled quentity controlled variable to, complete another one photovoltaic string by latter stage grid inverter MPPT controls.

The control method of a kind of dual input single tube Boost type photovoltaic interface changer the most according to claim 4, its feature It is: concrete rate-determining steps includes:

MPPT for first photovoltaic string controls: first distinguish output voltage and the electricity of this photovoltaic string in Sampling Interface changer Stream, constantly adjusts voltage reference u by power calculation_pv1,ref, by u_pv1,refWith sampled voltage u_pv1The error signal obtained is sent Entering actuator 1, the signal of actuator 1 output is sent into drive circuit after PWM, is produced PWM drive signal, uses In the shutoff of opening of control switching tube S, thus the MPPT realizing photovoltaic module 1 controls；

MPPT for another photovoltaic string controls: adjust again by sampling photovoltaic string output voltage, electric current and power calculation Whole voltage reference u_pv2,ref, by u_pv2, and sampled voltage u_pv2The error signal obtained sends into actuator 2, obtains output electricity after regulation Reference signal i of stream ring_o,ref, this controls outer shroud for MPPT；Further, by i_o,refWith output current sampling signal i_oObtain Error signal send into actuator 3, through overregulating the magnitude reference obtaining grid-connected current ring, then by this signal and and electrical network Voltage is multiplied with the unit sinusoidal signal of frequency homophase and obtains reference signal i of grid-connected current_g,ref, by this reference signal and grid-connected current Sampled signal i_g, the error signal asking difference to obtain sends into actuator 4, it is achieved the control of grid-connected current ring；Finally, actuator 4 is defeated The sinusoidal modulation signal gone out sends into drive circuit through SPWM modulation, produces SPWM and drives signal, is used for controlling rear class 4 switching tubes of DC/AC changer open shutoff, it is achieved thereby that photovoltaic module 2 MPPT control.

The control method of a kind of dual input single tube Boost type photovoltaic interface changer the most according to claim 1, its feature It is: described actuator 1, actuator 2, actuator 3, actuator 4 use the linear regulators such as PI, PID.